Gasoline containing sulfide ignition control agents



salts thereof formed through solid-solid reactions.

United States Patent 3,161,487 GASOLINE CONTAG SULFIDE IGNITION CONTROL AGENTS John J. Giammaria and Edwin M. Nygaard, Woodbury, N.J., assignors to Socony Mobil Oil Company Inc., a corporation of New York No Drawing. Filed Jan. 6, 1958, Ser. No. 707,108 4 Claims. (CI. 44-69) This invention relates to fuels for internal combustion engines of the spark-ignition type. It is more particularly concerned with fuels of this type that contain lead antiknock compounds. I

As is Well known to those familiar with the art, the addition of lead anti-knock compounds, such as tetraethyl lead to gasolines to increase their octane ratings, is a well-established practice. It is also well known, however, that the use of leaded gasolines has disadvantages, notably the occurrence of preignition. As the name implies, preignition is the ignition of the air-fuel mixture in the cylinder before the regular, timed spark-ignition. The engine will behave as if the spark had been advanced beyond its normal timing. This phenomenon is, of course, a barrier to further increases in compression ratio. Accordingly, the problem of preignition has become more acute, because of the trend to engines of increased compression ratio.

As it is contemplated herein, preignition is caused by incandescent particles of combustion chamber deposits. Such deposits consist of a mixture of carbonaceous material and lead salts formed by-decomposition of the lead anti-knock compound. The lead salts resulting from the combustion of a leaded motor fuel are complex in nature. It is believed they include lead chloride or bromide, lead oxide and lead sulfate, as well as mixed It has been foundthat these lead compounds have a catalytic effect upon the oxidation of the carbon in the combustion chamber deposits. The rapid oxidation of the carbon particles causes them to glow and to remain aglow for considerable periods of time after the combustion cycle. Accordingly, the glowing particles are present during the subsequent combustion cycle and cause preignition.

Pure carbonrmust be heated to about 1400 F. to make it glow. In the presence of lead salts, however, glow is initiated as much as 700 F. lower. It will be appreciated, therefore, that the presence of materials that will inhibit the catalytic oxidation effect of the lead salts will reduce preignition.

Ithas now been found that deposit induced preignition in spark-ignition internal combustion engines can be reduced simply and economically. It has been discovered that the addition of certain bis-(dialkoxyphosphinothioyl) sulfides and disulfides to leaded motor fuel will greatly reduce such preignition. Accordingly, it is an object of this invention to provide an improved fuel for internal combustion engines of the spark-ignition type. Another object is to provide an improved leaded gasoline. A specific object is to afford an improved gasoline containing a lead anti-knock compound and small amounts of certain bis-(dialkoxyphosphinothioyl); sulfides and disulfides. Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description.

Broadly stated, the present invention provides an improved leaded gasoline containing, a small amount, sufiiice , 2 cient to reduce preignition, of a compound having the formula:

R0 )n R0 S i2 wherein R is a lower alkyl group (1 to 8 carbon atoms per radical) and n is an integer varying between 1 and 2.

The fuels contemplated herein are mixtures of hydrocarbons suitable for use in internal combustion engines of the spark-ignition type. These fuels include both motor gasolines and aviation gasolines. In general, motor gasolines have an initial boiling point as low as about 80 F. and an end-boiling point as high as about 440 F. and boils substantially continuously between the initial boiling point and the end-boiling point. Aviation gasolines, on the other hand, are mixtures of hydrocarbons having an initial boiling point of about 80 F. and an end-boiling point of about 340 F. and boiling substantially continuously between these points.

At present, motor gasolines can contain up to about 3 ml. per gallon of a lead anti-knock compound, whereas aviation gasolines can contain up to about 4.6 ml. per gallon of the material. In general, the anti-knock compound is a gasoline-soluble lead compound. Accordingly, it is an organic lead compound. Typical materials are the lead tetraalkyls, such as lead tetraethyl and lead tetramethyl. Gasolines containing these compounds are commonly referred to as leaded gasolines.

It has been the practice to add the lead anti-knock compound together with a halohydrocarbon scavenger. Typical of these are ethylene dichloride, ethylene dibromide, acetylene tetrabromide, and hexachloropropylene. The scavenger can be a mixture of two or more compounds. Trus, for example, it is common practice to use a combiantion of ethylene dichloride and ethylene dibromide in leaded motor gasolines, whereas ethylene dibromide alone is used in leaded aviation gasolines.

The amounts of scavenger utilized are calculated to avoid excessivewear and corrosion ofthe operating parts of the engine, such as exhaust valves, and still achieve effective scavenging of leaddeposits. Thus, in the case of leaded motor gasolines, it has been the. practice to use one theory of ethylene dichloride and 0.5 theory of ethylene dibromide. On the other hand it has been the practice to use one theory of ethylene dibromide in leaded aviation gasoline. 'As used herein, one theory of a substance is the amount thereof required to convert all the lead present into a lead salt; in this case into lead chloride or bromide.

As has been mentioned hereinbefore, the lead salts, including the halides, present in the cylinder catalyze the oxidation of carbonaceous combustion chamber deposits to a state wherein they glow and cause preignition. It is the discovery of this invention that this catalytic action can be suppressed by the addition of certain bis-(dialkoxyphosphinothioyl) sulfides and disulfides to the leaded gasoline. These compounds have the generic structural formula:

P [RO/ sla wherein R is a lower alkyl radical having between land 8 carbon atoms and n is an integer, 1 or. 2. These compounds are named, throughout the specification and claims,

in accordance with the Report of the American Chemical Society Committee on Nomenclature Spelling and Pronunciation, which appeared in Chem. and Eng. News, vol. 30, No. 43, October 27, 1952, pages 4515-4522, inclusive. The particular types of compounds contemplated herein include bis-(dimethoxyphosphinothioyl) sulfide; bis(dimethoxyphosphinothioyl) disulfide; bis-(dibutoxyphosphinothioyl) sulfide; bis-(dibutoxyphosphinothioyl) disulfide; bis-(diamoxyphosphinothioyl) sulfide; bis-(dihexyloxyphosphinothioyl) disulfide; bis-(diheptyloxyphosphinothioyl) sulfide; bis-(dioctyloxyphosphinothioyl) sulfide; and bis-(dioctyloxyphosphinothioyl) disulfide.

The compounds utilizable herein are believed to be new compounds. The bis-(dialkoxyphosphinothioyl) sulfides are prepared in two steps. First four moles of an alcohol are reacted with one mole of P 5 at about 90 C. to produce the o,o-dialkylhydrogenphosphorodithioate,

Then, upon heating to 115-120 C. in dry xylene, this material is converted into the bis-(dialkoxyphosphinothioyl) sulfide. The bis-(dialkoxyphosphinothioyl) disulfide is prepared by oxidizing the o,o-dialkylhydrogenphosphorodithioate with nitrous acid at 2032 C.

The concentration of the organic bis-(dialkoxyphosphinothioyl) sulfide or disulfide to be added to the leaded gasolines will vary with the phosphorus content thereof. Concentrations can vary between about 0.0001 percent and about 2.0 percent, by weight of the gasoline. In preferred practice, between about 0.001 percent and about 0.1 percent, by weight, is used.

The gasoline composition of this invention can contain other additives in addition to the lead anti-knock compound, the halohydrocarbon scavengers, and the phosphonitrilic halide trimer. Thus, for example, these gasolines can include dyes; carburetor anti-icing agents, such as isopropyl alcohol and lauryl mercaptoacetic acid; corrosion inhibitors, such as polymerized fatty acids and salts of petroleum sulfonates; metal deactivators, such as N:N- disalicylidene-1,2-diaminopropane; and anti-gum formation additives, such as 2,6-ditertiarybutyl paracresol, N- normal butyl'para-amino-phenol, and N,N-disecondarybutylparaphenylenediamine.

The following examples are for the purpose of illustrating the preparation and the effectiveness of the compositions of this invention. It is to be understood that this invention is not to be limited by the specific compositions of the examples or to the operations and manipulations involved. Other additives as described hereinbefore can be used, as those skilled in the art will readily appreciate.

Example 1 the intermediate o,o-diisopropylhydrogenphosphorodithioate,

s (011) CHO] P It weighed 379.8 grams, a yield of 89%. Analysis. Found percent P: 14.9; percent S=28.7. Calculated percent P:l4.5; percent S=29.9.

4 Example 2 A solution of grams (0.47 mole) of the intermediate, prepared as set forth in Example 1, in 85.5 grams dry xylene were placed in a reaction vessel equipped with condensor and a nitrogen inlet tube. The solution was heated at 118 C. and sulfuric acid-dried nitrogen was bubbled through it for 35 minutes. Then, the clear xylene solution was decanted from a small amount of gummy solid and xylene was removed at 87 C. under 17 millimeters mercury pressure. The product, bis-(diisopropoxyphosphinothioyl) sulfide,

[(CH )zCH lzl -S- Hs)2l2 weighed 92 grams, a yield of 86.5%. Analysis.-Found percent S=27.9; percent P=15.1. Calculated percent S=24.4; percent P=15.7.

Example 3 To 128.4 grams (0.6 mole) of the intermediate product, prepared as set forth in Example 1, were added over a period of 10 minutes a cold solution of 24 grams (0.6 mole) sodium hydroxide in cc. of distilled water. The temperature during addition was 2628 C. The resulting sodium salt solution was filtered through diatomaceous earth and the filtrate transferred to a reaction vessel. Then, 41.4 grams (0.6 mole) sodium nitrite was dissolved in the sodium salt solution (the filtrate). Over a period of 54 minutes, 61.2 grams of 96% sulfuric acid (0.6 mole H 80 diluted with 60 cc. of distilled water was added to the salt solution. The reaction vessel was cooled, during this time, to maintain the reaction at 20-32 C. The product, bis-(diisopropoxyphosphinothioyl) disulfide,

was a yellow crystalline material. It was separated by filtration and washed with distilled water, 5% aqueous sodium carbonate solution, and again with distilled water. The crude product weighed 116.3 grams, a yield of 91%. This material was recrystallized from benzene and analyzed. Found: percent S=30.0, percent P=14.4. Calculated percent S=30.2, percent P=14.6.

PREIGNIT ION TESTING The effectiveness of additives to suppress the glow inducing eifect of lead salts on carbon was determined in a bench test. The test, which simulates the glowing efiiect of deposits from leaded fuel and lubricating oil, is conducted as follows:

A Vycor glass crucible (3.5" high and 1.5" in diameter) is placed upright in a close-fitting electric furnace. Pure carbon (0.1 g.) is placed in the bottom of the crucible and heated at 900 F. A blend of 4 ml. of test gasoline and 1.0 ml. of S.A.E. 30 grade lubricating oil is drawn into a hypodermic syringe. This is mounted on a metering device adjusted to deliver 2.0 ml. in 15 minutes. The blend is slowly dropped on the hot carbon and the glowing tendency of the carbon is observed during the addition (15 min.) and for 5 minutes thereafter.

The test gasoline was a 10 percent high boiling end of unleaded, cracked commercial gasoline to which was added tetraethyl lead in an amount of 2.5 ml./ 100 ml. of residue. This gasoline, when tested as aforedescribed, caused the carbon to glow throughout the addition of the leaded fueloil blend and after addition, until all the carbon was burned off. The effectiveness of a preignition suppressant was determined by blending various amounts with the leaded gasoline and testing each blend. The minimum theory (one theory: amount of additive to furnish 2 atoms of phosphorus per 3 atoms of lead in the fuel) required to suppress the glowing completely was determined by testing the blends.

Using the test fuel (leaded) as aforedescribed, blends were made up containing various amounts (theories) of typical compounds contemplated in this invention. The minimum theory for each additive was determined in the aforedescribed test. The compound names and the minimum theory of each to suppress glow in this test are set forth in the table.

TABLE Minimum Theory Example No. Compound Blended in Gasoline Required to Suppress Glow 2 Bis-(diisopropoxyphosphinothio l) disulfide I 0. 30 3 Bis-(diisopropoxyphosphinothioyl) sulfide 0.35

mula,

[RO\P i R 0 \S .12

wherein R is a lower alkyl group and n is an integer varying between 1 and 2.

2. A leaded gasoline containing between about 0.0001 percent and about 2.0 percent, by weight of the gasoline of a compound having the formula [RO\ I P RO \B |1 wherein R is a lower alkyl group and n is an integer varying between 1 and 2.

3. A leaded gasoline containing between about 0.0001 percent and about 2.0 percent, by weight of the gasoline, of bis-(diiospropoxyphosphinothioyl) sulfide.

4. A leaded gasoline containing between about 0.0001 percent and about 2.0 percent, by weight of the gasoline, of bis-(diiospropoxyphosphinothioyl) disulfide.

References Cited in the file of this patent UNITED STATES PATENTS 1,763,852 Johnson June 17, 1930 2,198,915 MacAfee Apr. 30, 1940 2,523,147 Dean et a1 Sept. 19, 1950 2,705,694 Bartlett et al Apr. 5, 1955 2,765,220 Yust et a1. Oct. 2, 1956 2,794,719 Bartleson June 4, 1957 2,897,068 Pellegrini et a1 July 28, 1959 FOREIGN PATENTS 767,018 Great Britain Jan. 30, 1957 1,123,123 France June 4, 1956 

1. A LEADED GASOLINE CONTAINING A SMALL AMOUNT, SUFFICIENT TO REDUCE PREIGNITION, OF A COMPOUND HAVING THE FORMULA, 